JPH0776420B2 - Sputtering film forming method and film forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sputtering film forming method and apparatus.

2. Description of the Related Art Reactive sputtering, in which a target material and a sputtering gas component are chemically reacted with each other to form a thin film of these compounds during sputtering film formation, is widely used for forming a metal nitride or oxide film ( For example, Shigeru Hayakawa et al. "Thin film technology"
(S57.12.1), Kyoritsu Shuppan, P18).

Problems to be Solved by the Invention
The film formation by sputtering will be described as an example.

FIG. 5 shows a known load lock type sputtering apparatus. 1
Is a load lock chamber for the non-deposited substrate 2 on the input side, 3 is a sputter chamber, and 4 is a load lock chamber for the outgoing side of the deposited substrate 5. 6,
Reference numerals 7, 8 and 9 are known gate valves for passing the substrate. 10 is a Te target, and 11 is a known magnet.
Reference numeral 12 is a variable voltage power source for giving a negative DC voltage to the target, and 13 is a power controller for controlling the output voltage of the variable voltage power source. Reference numeral 14 is a rotary shaft that holds the substrate 15 and rotates it by means not shown.

Reference numeral 16 is a tube for supplying Ar and O ₂ to the sputtering chamber 3. In this figure, well-known exhaust and leak means, substrate transfer means, target cooling means, film thickness meter and the like which are usually required for the sputtering apparatus are omitted.

Next, the operation will be described. Application of electric power (voltage) to the target 10 has a rectangular wave shape as shown in FIG. Substrate
When the time when the film formation on 15 is completed is B, by the time until the next A, “the substrate 15 is removed from the rotation shaft 14 and transferred to the exit side load lock chamber 4 through the gate valve 8 and the substrate 2 Is transferred to the sputter chamber 3 through the gate valve 7 and the rotating shaft 14
Is held and rotated. " During the above operation, the power controller 13 sets the variable voltage power source to a low power level in which the film is not attached to the substrates 5 and 2 and the discharge is not stopped.
Control 12 outputs.

During the period from A to B, the power controller 13 controls the output of the variable voltage power source 12 to a high power level which is sufficient to form a film on the substrate.

When power is applied to the target 10 as described above, the surface temperature of the target 10 is low at the beginning of the film deposition on the substrate, as shown in FIG. It rises, and when film formation is completed, it falls exponentially and changes into a sawtooth shape. The time constant when the temperature rises and falls increases as the heat capacity of the target with respect to the power applied to the target 10 increases, and the rise and fall of the temperature become slower.

When the surface temperature of the target 10 is low, it is a reactive gas.
Since the reaction with O ₂ is not so active, the oxygen concentration of the oxide layer formed on the target surface becomes low, and when the surface temperature is high, the oxygen concentration of the oxide layer on the target surface becomes high. When the oxidized Te target is sputtered with Ar ions, the energy of Ar ions is also consumed to separate Te and oxygen, so the higher the oxygen concentration in the oxide layer, the lower the Te sputtering rate. When the sputtering rate of Te is low, the chances of Te and oxygen reacting with each other on the substrate surface increase, so the concentration of oxygen contained in the film becomes high, and conversely, when the sputtering rate becomes high, the concentration of oxygen contained in the film becomes low.

FIG. 8 shows the result of AES analysis of the TeOx film formed on the resin substrate as described above. It can be seen that the oxygen concentration is low at and near the interface between the TeOx film and the substrate.
C in FIG. 8 is carbon contained in the resin substrate.

When the oxygen concentration of the TeOx film becomes low, there is a problem that the film is corroded by moisture in the atmosphere and the characteristics of the optical disk as a recording film are deteriorated, and normal signal recording or reproduction cannot be performed.

In order to solve this problem, a shutter is provided between the target 10 and the substrate, the power applied to the target 10 is constantly maintained at a high power level to keep the target surface temperature constant, and the rotation axis 14 of the substrate is There is also a method to prevent the film from sticking to the substrate during desorption and transfer of the substrate.
Is used less efficiently, the consumption is faster, and the film is thickly attached to the shutter, so that the film is easily peeled off from the shutter, and the inside of the sputtering chamber 3 is contaminated with the peeled film to cause a defect in the film. There was a problem that was not practical.

Therefore, the present invention is, for example, to prevent the oxygen concentration from changing in the thickness direction of the TeOx film, that is, the composition ratio not to change in the thickness direction of the film in reactive sputtering.

Means for Solving the Problems And technical means of the present invention for solving the above problems,
As the film is deposited on the substrate, the reactive gas partial pressure / inert gas partial pressure (hereinafter abbreviated as partial pressure ratio) or the reactive gas flow rate / inert gas flow rate (hereinafter abbreviated as flow rate ratio) is reduced.

Action The action of this technical means is as follows for the TeOx film. When the partial pressure ratio or the flow rate ratio is reduced, the amount of O ₂ gas decreases.

Then, as the temperature of the target surface rises, Te
The increase in the reactive gas concentration in the film due to the decrease in the sputter rate is offset. Then, the oxygen concentration contained in the film also becomes substantially constant.

As a result, it becomes possible to form a film in which the oxygen concentration does not easily change in the film thickness direction.

Embodiment One embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, in which the same components as in FIG. 5 showing a conventional example are designated by the same reference numerals.

Unconventional place the known O ₂ flow regulating valve 20 for adjusting the O ₂ flow, a known Ar flow rate adjusting valve 21 for adjusting the Ar flow rate was controlled at a gas flow rate regulator 22, for example, the flow rate of Ar is constant At O ₂
The flow rate is controlled so as to decrease in a substantially exponential manner from the start of film formation as shown in FIG.

By reducing the O ₂ flow rate, the gas partial pressure ratio and the gas flow rate ratio are reduced, and the amount of O ₂ gas is reduced. Then, the chances of Te and oxygen reacting with each other on the surface of the substrate 15 are reduced, so that the concentration of oxygen contained in the film becomes low and the conventional change in oxygen concentration is offset.

Therefore, the TeOx film 23 thus formed has a third
As can be seen from the AES analysis results shown in the figure, there is no change in the oxygen concentration in the film thickness direction.

Note that the change in the O ₂ flow rate between B and A in FIG. 2 is due to the return operation for increasing the O ₂ flow rate that has dropped to a predetermined value at the end of film formation to a predetermined value at the start of film formation. is there. The change in the flow rate at the time of restoration may be linear as shown in FIG. 2 or not shown, but may be stepwise or another method.

Next, another embodiment of the present invention will be described.

Although the O ₂ flow rate is controlled to decrease in an approximately exponential function in the above-described embodiment, the exponential function may be approximated by a broken line. Then, the circuit configuration can be simplified. Further, when the composition ratio is not required to be so strict, it may be approximated by one straight line as shown in FIG.

When only the O ₂ flow rate is changed as in the above embodiment, the total pressure in the sputter chamber 3 changes if the amount of gas exhausted from the sputter chamber 3 is constant. If the influence of the change in the total pressure on the film formation cannot be ignored, the sputtering chamber 3 is evacuated through a known conductance valve (not shown) so that the total pressure in the sputtering chamber 3 becomes constant. The opening may be adjusted. Alternatively, the flow rate of Ar may be changed so that the total pressure in the sputtering chamber 3 becomes constant.

The power supply for supplying power to the target 10 is not limited to direct current, and may be a high frequency power supply.

Further, even at a low power level, a shutter may be provided if the attachment / detachment of the substrate to / from the rotary shaft 14 and the film adhesion to the substrate cannot be ignored during the transfer of the substrate.

The sputtering method is not limited to magnetron sputtering, and also in known so-called ion beam sputtering in which ions generated from an ion source are accelerated to collide with a target to perform sputtering, by changing the partial pressure ratio or the flow rate ratio. The above effect can be obtained.

The target material is not limited to Te, and may be another metal or alloy, nonmetal, or compound.

The inert gas is not limited to Ar, and the reactive gas is not limited to oxygen.

EFFECTS OF THE INVENTION In the reactive sputtering film formation, the reactive gas partial pressure / inert gas partial pressure or the reactive gas flow rate / inert gas flow rate is decreased as the film is deposited on the substrate.

By reducing the gas partial pressure ratio or the gas flow rate ratio, the amount of the reactive gas is reduced. Then, the chances that the target material reacts with the reactive gas on the surface of the substrate decreases, so that the concentration of the reactive gas component contained in the film becomes thin.

As a result, it is possible to offset the increase in the reactive gas component concentration caused by the decrease in the sputter rate accompanying the change in the target temperature due to the sputtering power application and to form a film in which the composition ratio does not change in the thickness direction of the film. Corrosion resistance can be improved in a TeOx film which is an optical disk recording film.

[Brief description of drawings]

FIG. 1 is a front view conceptually showing one embodiment of the present invention, and FIG.
FIG. 4 is an explanatory view of the O ₂ flow rate change state of FIG. 1, FIG. 3 is an AES analysis result explanation view of the film formed by applying the present invention, and FIG. 4 is a change of the O ₂ flow rate in other examples. FIG. 5 is a front view conceptually showing a conventional example, FIG. 6 is a change state explanatory view of electric power applied to the target of FIG. 5, and FIG. 7 is a target surface temperature of FIG. Change state explanatory drawing, 8th
The figure is an explanatory view of the AES analysis result of the film formed by the conventional method. 3 ... Sputtering chamber, 10 ... Target, 11 ... Magnet, 15 ... Substrate, 20 ... O ₂ flow rate adjusting valve, 21 ... Ar flow rate adjusting valve, 22 ... Gas flow rate controller.

Claims (3)

[Claims] 1. In reactive sputtering film formation, as the film formation progresses, the reactive gas partial pressure / the reactive gas partial pressure are set so as to offset the increase in the reactive gas concentration in the film due to the decrease in the sputter rate accompanying the temperature increase of the target. A sputtering film forming method in which the composition ratio change in the film thickness direction is suppressed by reducing the inert gas partial pressure or the reactive gas flow rate / inert gas flow rate. 2. An inert gas supply means for supplying an inert gas into the vacuum container, a reactive gas supply means for supplying a reactive gas, a target and a substrate provided in the vacuum container, and an electric power supply. Sputtering means for receiving and ionizing the gas, sputtering the target with the ions, and depositing particles ejected from the target as a film on the substrate; and the inert gas supply means as the film is deposited on the substrate. And at least one of the reactive gas supply means to change the gas flow rate to reduce the reactive gas partial pressure / inert gas partial pressure or the reactive gas flow rate / inert gas flow rate. The gas flow rate control means has a reactive gas partial pressure / inert gas partial pressure as the film formation progresses in order to suppress the composition ratio change in the film thickness direction. Or the reactive gas flow rate / inert gas flow rate is controlled to be small so as to offset the increase in the reactive gas concentration in the film due to the decrease in the sputter rate accompanying the temperature increase of the target. . 3. The gas flow rate control means controls the reactive gas partial pressure / inert gas partial pressure or the reactive gas flow rate / inert gas flow rate so as to decrease in an approximately exponential manner. The sputtering film forming apparatus according to item 2 above.